Horneous (Hard) Endosperm
The horneous (hard) endosperm test measures the percent of horneous or hard endosperm out of the total endosperm in a kernel, with a potential value from 70 to 100%. The greater the amount of horneous endosperm relative to soft endosperm, the harder the corn kernel is said to be. The degree of hardness is important depending on the type of processing. Hard corn is needed to produce high yields of large flaking grits in dry milling. Medium-high to medium hardness is desired for alkaline cooking. Moderate to soft hardness is used for wet milling and livestock feeding.
Hardness has been correlated to breakage susceptibility, feed utilization/efficiency, and starch digestibility. As a test of overall hardness, there is no good or bad value for horneous endosperm; there is only a preference by different end users for particular ranges. Many dry millers and alkaline cookers would like greater than 90% horneous endosperm, while wet millers and feeders would typically like values between 70 and 85%. However, there are certainly exceptions in user preference.
Average U.S. Aggregate horneous endosperm (79%) in 2016 was same as 2015, and lower than 2014 (82%) and 5YA (83%).
U.S. Aggregate standard deviation for horneous endosperm was 4%, higher than 2015 (3%), but same as 2014 and 5YA (both 4%).
The 2016 horneous endosperm range (71 to 93%) was slightly lower than 2015 (71 to 95%) and 2014 (71 to 97%).
Of the 2016 samples, 60.4% contained less than 80% horneous endosperm, which was similar to 2015 (61%) and much higher than 2014 (38%). This distribution indicates a higher percentage of corn samples with soft endosperm in 2016 and 2015 than in 2014.
Average horneous endosperm was uniform across the Gulf, Pacific Northwest, and Southern Rail ECAs, with an average of 79%, 79%, and 80% for the three ECAs, respectively.
The figure on the adjacent page shows a weak but positive relationship (a correlation coefficient of 0.70) between horneous endosperm and true density for the 2016 samples.
The second figure shows the average U.S. Aggregate horneous endosperm and true density values over the past six years. This illustrates that average U.S. Aggregate horneous endosperm increases with true density (with a correlation coefficient of 0.88); thus, horneous endosperm tends to be higher in years when average true density is higher.